/*
* opencog/atoms/value/ContainerValue.h
*
* Copyright (C) 2020, 2025 Linas Vepstas
* All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License v3 as
* published by the Free Software Foundation and including the exceptions
* at http://opencog.org/wiki/Licenses
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program; if not, write to:
* Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#ifndef _OPENCOG_CONTAINER_VALUE_H
#define _OPENCOG_CONTAINER_VALUE_H
#include <opencog/atoms/value/LinkValue.h>
#include <opencog/atoms/atom_types/atom_types.h>
namespace opencog
{
/** \addtogroup grp_atomspace
* @{
*/
/**
* ContainerValues provide a thread-safe containers for Values. They
* provide a producer-consumer API, where the produced values are to
* added to the container (possibly from multiple threads) and are
* removed by consumers (possibly in other threads.)
*
* It provides a uniform API for all such containers, i.e. both queues
* and sets, for code that wants to handle either type (e.g. for
* queries.) The add() method will append to the end of a queue,
* or, for sets, insert into the set, while remove() will remove from
* the head of a queue, or, for sets, remove in whatever order the set
* pool provides (using std::less by default.)
*
* Semantics include open() and close(). The close() method allows the
* producer to tell consumers that it's done adding things. i.e. its
* an end-of-stream indicator. (XXX Maybe this should be moved to the
* LinkStreamValue base class ??)
*/
class ContainerValue
: public LinkValue
{
protected:
ContainerValue(Type t) : LinkValue(t) {}
public:
ContainerValue(void) : LinkValue(CONTAINER_VALUE) {}
virtual ~ContainerValue() {}
virtual void open(void) = 0;
virtual void close(void) = 0;
virtual bool is_closed(void) const = 0;
virtual void add(const ValuePtr&) = 0;
virtual void add(ValuePtr&&) = 0;
virtual ValuePtr remove(void) = 0;
virtual void clear(void) = 0;
virtual std::string to_string(const std::string& = "") const;
virtual bool operator==(const Value&) const;
virtual bool operator<(const Value&) const;
};
VALUE_PTR_DECL(ContainerValue);
/** @}*/
} // namespace opencog
#endif // _OPENCOG_CONTAINER_VALUE_H